By Nathalie Gee
No matter where you go in the US, fresh water costs money. Each American uses an average of 82 gallons of water a day at home and the average family spends more than $1,000 per year in water costs. In places like California, where they count every drop of seasonal rain, access to fresh water is getting more and more unreliable. So individuals and homeowners continue to look for ways to save water on their landscaping. We are ripping out lawns, planting drought-tolerant, native plants, and questioning now, What’s the best method to water my plants in a warming world? As droughts deepen and water costs rise, it may be time for homeowners to phase out the traditional sprinkler system and install a drip irrigation system, the water-saving alternative.
Drip (or trickle) irrigation systems differ from typical sprinkler (surface) systems in that they feed water slowly, directly on the roots of plants, as opposed to spraying water on top of plant foliage and allowing the water to reach roots via gravity. A drip irrigation system uses a system of hoses attached to a water source and distributed throughout your garden. It is intended to disperse water slowly and evenly, and to conserve water. Hoses seep water slowly below the soil surface (or sometimes right at the surface), delivering water directly into the root zone, minimizing evaporation.
Some experts estimate that as much as 50 percent of water used for irrigation is wasted due to evaporation, wind, or runoff caused by inefficient irrigation methods and systems.
By supplying only the amount of water needed by your plants, less overspray and runoff make their way into local drainage systems, reducing groundwater pollution. (Note that excess nutrients from fertilizers in wastewater and stormwater runoff contribute to algal blooms that can wreak havoc on local waterways, damage fisheries, and threaten municipal water supplies.) Drip irrigation systems have advantages in a wide variety of use cases, from garden beds and potted plants to growing commercial crops.
Mechanics of a drip irrigation system
While there is variation between custom systems and consumer kits, the main components of a residential drip irrigation system remain the same. The essential components include
- An on/off valve
- Backflow preventer
- Pressure regulator
- Connection fittings
The valve lets you turn the water on and off, automatically or manually. Mechanical and digital controllers can automate the delivery of water on a preset schedule. WaterSense certified control systems and timers can adapt to plants’ needs, shutting off or delaying watering cycles in response to rain, freezing temperatures, or high winds. According to the EPA, a WaterSense controller can save the average household 7,600 gallons of water per year, and rebates are available to help homeowners install new systems or make the switch.
The backflow preventer keeps water flowing and stops contamination of the water source, while the pressure regulator maintains low-pressure water flow. The filter prevents clogging from sediment and debris. Tubingand connectors form the distribution system.
Soaker hoses made of permeable rubber deliver water along their entire length. They are easy to lay out in heavily planted areas, but will deliver less water at the distal end. And the permeable hoses are often made from recycled tires, which are suspect for their toxicity. Some soaker hoses are solid, but have tiny cuts at regular spacing. Dripperline is a more robust solution, using micro emitters pre-installed at regular spacing. Drip tape is larger in diameter and delivers water along its length, but is seen more in commercial agriculture or community gardens.
Drip irrigation systems can also use solid mainlines with individual emitters and “spaghetti tubing” added manually to deliver water to select locations. Installing large numbers of tubes and emitter fittings is labor-intensive. These types of systems are ideal for getting plants and young trees and shrubs established, before they’re largely water-independent.
Consider the drawbacks
Drip irrigation systems can have a high upfront cost. On average, homeowners can expect to pay anywhere from $350 for a drip irrigation system to thousands of dollars to hire a professional contractor instead of DIY. For larger acreages, setting up water supply mains and extensive tubing can, of course, be much more expensive. Additionally, most commercially available systems are made of plastic, especially polypropylene, which can negatively impact soil fertility. One way to reduce the amount of plastic used in a drip irrigation system is to plant drought resistant or native crops and plants that already require little water. This will reduce the size of the system and its overall water needs.
As with most outdoor equipment, a drip irrigation system will require regular maintenance. Even with maintenance the system will degrade eventually. Tubes and fittings exposed to UV radiation from the sun and at risk of freezing and splitting while overwintering will break down more quickly. Some tubing can last upwards of ten years if buried.
Mineralization and particles can clog emitters if they are not flushed (manually or automatically) on a regular basis, also causing system failures. Finally, humans, dogs, vermin, and ground squirrels can cause breakage or failure in tubing in- and aboveground. (Important: be careful where you dig!) Be sure to regularly check that the system is watering as expected and maintain it well to ensure the system’s longevity and preserve expensive plantings.
Greywater drip irrigation systems
In places with strict outdoor water-use mandates, such as Southern California, many homeowners turn to irrigating their gardens with greywater. Greywater is any type of “used” water that does not include food, toxic chemicals, or human waste. Water from your shower, washing machine, dishwasher, or faucet can be repurposed for irrigation. Most greywater contains some dirt, soap, and related chemicals like nitrogen and phosphorus, and with the appropriate filtration setup this is fine for most plants. (Check out Elemental Green’s picks for greywater-safe cleaning products.)
Because greywater is not safe for human contact, it is not used for surface watering. A successful greywater drip irrigation system requires a filter and tubing specifically designed for greywater. There are two types of filters that remove particles: manually cleaned filters, which tend to be lower cost, and automatic filters, which are less maintenance but can be more expensive. The most common reason for greywater irrigation problems is failure to maintain manual filtration systems. It’s important to consider both options and contact an installer whenever possible, prior to committing to a greywater system for your home.
Typically, our drains take all wastewater directly to the sewer system, even though it’s not sewage. Capturing greywater can help your garden thrive while cutting your household’s outdoor water use. Water is a precious resource growing scarcer by the year. But using (and reusing) water wisely can nurture plants that produce food, support wildlife, or simply add beauty to the landscape. Homeowners wanting to both save on water bills and conserve fresh water resources can make a difference… drip by drip.
Nathalie Gee is a recent graduate of Barnard College of Columbia University, where she majored in environmental science. She is a freelance writer focused on sustainability and climate topics.
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